This invention relates generally, as indicated, to a reflector and light system, and more particularly, to such a system which provides a relatively compact, optically efficient and cost effective light source for a target, especially a relatively tight target such as a fiber optics light pipe or the like that requires the light to strike the target at a minimum acceptance angle.
Because of the increased use of fiber optics light pipes and the like to transmit light, there is an increasing need for a more efficient light source for the transmitted light. Fiber optics light pipes generally consist of one or more strands of glass or plastic fibers which may be used for a wide variety of applications, including inspection lighting, ultraviolet curing, phototherapy, instrumentation, clean rooms, and fiberscopes and the like.
It is generally known from U.S. Pat. No. 4,241,382 to provide an illuminator in the form of a light bulb having a fiber optics coupler as an integral part of the envelope. The bulb is provided with a combination of ellipsoidal and spherical mirrors which direct the light through an optical window to a fiber optics light pipe or the like. To facilitate trapping of the light in the optical fibers, the light may be caused to emerge from the optical window at angles equal to or less than the critical angle of the fibers.
The critical angle is the maximum angle of incidence of the light rays striking the fibers that will experience total internal reflection within the fibers. Therefore, all of the light that is focused on the fibers must strike the fiber ends at angles equal to or less than the critical angle or that portion of the light which does not will not be transmitted by the fibers.
Although the illuminator of the aforementioned U.S. Pat. No. 4,241,382 accounts for the critical angle, such illuminator does not effectively account for the attenuation of the light in the fibers. When light is transmitted through an absorbing medium, the irradiance decreases exponentially with the distance of transmission. The distance light must travel within optical fibers is inversely proportional to the cosine of the angle that the light enters the fibers. Therefore, a light source that directs light at a target at a minimum acceptance angle would be optimal.
To achieve a small acceptance angle with the illuminator of U.S. Pat. No. 4,241,382 would require an increase in the distance between the filament and the optical window, which has the objection that the overall dimensions of the illuminator would have to be increased exponentially. Also, increasing such distance would cause the distance between the filament and the ellipsoidal surface to decrease. As the filament nears the ellipsoidal surface, defocus occurs causing a greater percentage of the light to be reflected at non-collectable angles or reflected back into the filament. Therefore, there is a minimum average acceptance angle that this particular illuminator can produce.
British Patent Specification No. 763,376, published Dec. 12, 1956, discloses a multi-reflector system that addresses some of these problems by providing a rearwardly facing reflector that reflects the light back onto a forwardly facing reflector that in turn reflects the light forwardly in a parallel beam. However, this system has the drawback that the focal point for the forwardly facing reflector is within the reflector system itself. Also, the forwardly facing reflector reflects the light as a parallel beam, which makes it difficult to focus the light on a relatively tight target outside the reflector, and the light is reflected back through the light source which blocks out a large percentage of the light before it reaches the target.